Learn to read Japanese and Korean script with automatic flashcards

Why Koji

I wanted to learn how to read Japanese and Korean quickly and easily. Koji determines what syllables — and then which words — you're ready to learn based on the characters and syllables you've already mastered. Simple, automatic.

This is a free tool I built for myself and anyone else who wants to learn. All pronunciation audio is recorded by professional voice artists — no robotic text-to-speech.

How it works

1. 1 Learn new characters — each session introduces a small batch of characters with their romanised readings and audio.
2. 2 Review with flashcards — press Space to reveal the answer, then grade yourself A Again or G Good.
3. 3 Spaced repetition does the rest — characters you find easy appear less often; ones you struggle with come back sooner. Come back when cards are due to keep your memory fresh.
4. 4 Unlock syllables — once you've mastered the right characters, syllables that use those characters are automatically unlocked for you to learn.
5. 5 Build up to words — once you've mastered the right syllables, full words using those syllables are unlocked so you can read real text.

Cram mode

Sometimes you don't want to wait for cards to come due. You just want to drill the ones giving you trouble. Cram takes every card you've reviewed, sorts them by how much you've struggled, and lets you run through them back to back.

Space to reveal, N to move on. It loops when you reach the end.

Managing cards

• • Use the ⋮ menu on any review card to manage it.
• • Move to New Cards — sends a card back to the new cards queue so you can start fresh.
• • Retire — hides a mastered card from reviews. You can unretire cards from the Stats page.

The Name

Koji is a fungus used in Japanese brewing. It's what turns grain into miso, sake, soy sauce. Without it, none of those exist.

The interesting bit is how it grows. Koji spreads through branching networks of mycelium, reaching toward nutrients, thickening the connections it uses most. The ones it doesn't use die off.

Your brain works the same way. When you learn a new character, dendrites branch out and form connections. Review that character, and those pathways strengthen. Neglect it, and they get pruned. Spaced repetition works with this biology rather than against it, feeding your memory at the intervals where it matters.

That's where the name comes from. And the little grain you'll see around the app? That's Kōji-kun. He started as a plain grain, went through the whole fermentation process, and came out the other side. He shows up to remind you the growth is happening, even when it doesn't feel like it.